In the operation of relatively large fuel burners it has been past practice to provide a safety checking device or circuit that would shut down the burner in a safe manner and would lock out thereby requiring manual reset before the burner could be restarted. Most of the lockout devices utilized have been of the thermal type that require 10 to 15 seconds of improper operation before they respond and turn off the burner. In most burner sequencing equipment, the shut down occurs in the event that a flame is sensed by a flame sensing means when none should be present, or no flame is sensed when a flame should be present. The delay allowed by the thermal type safety lockout devices is undesirable. In addition, the point at which the system had failed, thereby indicating what portion of the burner cycle is defective, has not been readily indicated. If it is desirable to know at what point the burner malfunctioned, it is normally necessary to add additional indicating equipment.
Magnetic type lockout devices have been used in place of thermal type lockout devices. This overcomes the delay, but the magnetic type lockouts have not provided the safety checking feature incorporated in the present invention.